I have developed a general perpose shield that adds an extra ATMega328(info.protoneer.com/2) to your setup. Currently I program the secondaryMCU with the ArduinoISP sketch. This works fine but I would like to add a USB port to it so you can program and send serial commands independently to the secondary MCU shield.

The ATMega32U4 would work well for this and because the Leonardo is based on it,it would add full compatibility for my shield.

What would be the bare minimum components needed to make a board that is Leonardo compatible?

I am planning doing this myself, you can remove the extra led's and the power stuff if you plan on only using USB power, maybe L1 which is a ferrite bead to help clean up the analog input voltage, but there is not really that much to it

I am planning doing this myself, you can remove the extra led's and the power stuff if you plan on only using USB power, maybe L1 which is a ferrite bead to help clean up the analog input voltage, but there is not really that much to it

Yes... there are a bunch that can be removed. Would you be interested in teaming up with me to get this solved?

I have also looked at : http://imall.iteadstudio.com/itaeduino-leonardo.html - Have a look under downloads for the schematics